// 顶点
// 表面着色器 开发速度快
// 连连看，上手容易

Shader "Custom/VertexShader"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
    }
    SubShader
    {
        Tags { "RenderType"="Opaque" }
        LOD 100
        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "UnityCG.cginc"
            #include "Lighting.cginc"
            struct appdata
            {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
                float3 normal : NORMAL;  
            };
            struct v2f
            {
                float2 uv : TEXCOORD0;
                float4 vertex : SV_POSITION;
                float3 worldNormal : TEXCOORD1;
                float3 worldPos : TEXCOORD2;
            };
            sampler2D _MainTex;
            float4 _MainTex_ST;
            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = TRANSFORM_TEX(v.uv, _MainTex);
                o.worldNormal = UnityObjectToWorldNormal(v.normal);
                o.worldPos = mul(unity_ObjectToWorld, v.vertex).xyz;
                return o; 
            }

            fixed4 frag (v2f i) : SV_Target
            {
                fixed3 worldNormal = normalize(i.worldNormal);
                fixed3 worldLightDir = normalize(UnityWorldSpaceLightDir(i.worldPos));
                fixed3 albedo = tex2D(_MainTex, i.uv).rgb;
                fixed3 ambient = UNITY_LIGHTMODEL_AMBIENT.rgb * albedo;
                fixed3 diffuse = _LightColor0.rgb * albedo * max(0, dot(worldNormal, worldLightDir));
                return fixed4(ambient + diffuse, 1.0);
            }
            ENDCG

        }
    }
}